The present invention relates to a torque measuring device for measuring a rotation rate and a torque of a a member of body to be measured such as rotating machine with a non-contact access at a remote portion.
A conventional art for measuring the torque of the rotating machine with a non-contact access is disclosed in Japanese Patent Laid-open Publication No. HEI 6-34462 as xe2x80x9ca torque detecting devicexe2x80x9d. This torque detecting device detects the torque generated in a shaft portion of a power transmission device of an automobile, for example.
FIG. 29 shows an arrangement of this torque detecting device. As shown in FIG. 29, a torque detecting device is provided with a linear optical reflector 2 for efficiently reflecting a light on an outer circumferential surface of a shaft 1 as a body of rotation to be measured. A first detecting portion 3 and a second detecting portion 4 are disposed so as to be opposed to the linear optical reflector 2 and are provided with light emitting elements 3a and 4a, and light receiving elements 3b and 4b, respectively. These detecting portions 3 and 4 has structures for generating lights towards different two positions in an axial direction of the shaft 1 by the light emitting elements 3a and 4a and to detect the reflected lights by the light receiving elements 3b and 4b. 
Thus, rotation of the shaft 1 allows the light receiving elements 3b and 4b to detect signals obtained from the optical reflector 2 for every rotation period. The detected signals are formed by a waveform adjusting circuit to gain a pulse signal from the light receiving element 3b and a pulse signal of the light receiving element 4b, as shown in FIG. 30. A period T of the pulse signal represents the rotation time for the period. Further, by using a delay time t of the pulse signal of the receiving element 4b against the pulse signal of the receiving element 3b, the torque Ft can be calculated according to the following mathematical equation (1) as below.
(Mathematical Equation 1)
Ft=2xcfx80Kxxc2x7t/Txe2x80x83xe2x80x83(1)
K: twisted spring constant of shaft 1
X: measured distance between two positions
Thus, the above-mentioned torque detecting device irradiates the light from the light emitting elements 3a and 4a to the shaft 1 and receives the light reflected by the optical reflector 2 at the light receiving elements 3b and 4b. Then, based on the detected signals from the optical reflector 2 as shown in FIG. 31, the torque detecting device generates a pulse signal shown in FIG. 30 so as to calculate the rotation rate and the torque from a period of this pulse signal.
The conventional art for measuring the torque of the rotating machine is disclosed in Japanese Patent Laid-open Publication No. HEI 7-325095 as xe2x80x9ca rotation rate measuring devicexe2x80x9d.
FIG. 32 shows a diagram of this rotation rate measuring device. In FIG. 32, only major portions are given with reference numerals. In the rotation rate measuring device shown in FIG. 32, a light from a laser diode 5, which is generated in shape of pulse at a predetermined frequency, is made into a parallel light by a collimeter lens 6, and the light is then irradiated as the parallel light to a rotation member or body 7 to be measured. Since the reflecting light of the irradiated light is varied depending on irregularities 8 or the like, which are formed on the surface of the rotation body 7, the intensity of the reflected light changes according to the rotation of the rotation member 7.
In the rotation rate measuring device in FIG. 32, the thus reflected light is received by a photodiode 10 by using a lens 9 and the rotation rate is calculated through the signal processing of this received signal. In the signal processing, at first, the rotation ratemeasuring device extracts the signal of the reflected light of the laser beam, which is given with pulse modulation, by a bandpass filter (BPF) 11. The bandpass filter (BPF) 11 passes frequency component of 500 kHz therethrough. Then, a low pass filter (LPF) 12 removes a signal component with a high frequency. After removing the signal component with a high frequency, the change of time becomes the change of intensity for the reflected light, corresponding to the rotation period of the rotation body 7.
Next, a control circuit 13 digitizes the signal to give the fast Fourier transform action to the signal. Then, a frequency distribution can be measured as shown in FIG. 33. The rotation frequency of the rotation body 7 becomes a frequency f0, which has a large distribution frequency. In this case, the rotation frequency T is 1/f0.
When calculating the torque, this rotation rate measuring devices should be set on two positions. In this case, a delay time t of a detection signal shown in FIG. 30 can be gained according to a mathematical equation (2), so that the torque can be calculated by using the following mathematical equation (1).
(Mathematical Equation 2)
t=|1/f1xe2x88x921/f0|xe2x80x83xe2x80x83(2)
f1: rotation frequency, which is calculated by other rotation rate measuring device
However, in the torque detecting device mentioned hereinbefore for measuring the torque of the rotation machine with the non-contact state, a rising time of a detection signal shown in FIG. 31 is usually defined by about several tens of xcexcm. Accordingly, it is not possible to generate a pulse signal at an accuracy in time higher than this rising time and to obtain a frequency of the pulse signal. Therefore, in the case that the rotation rate is minutely varied for every rotation, there is a problem such that the rotation rate and the torque for every rotation is not obtainable with a high accuracy. For example, there is an expectation for a generator having an axis diameter of 850 mm and the rotation rate of 3000 rpm to obtain the torque by calculating the frequency of the pulse signal with a measuring accuracy of 100 ns for every rotation in order to monitor a generation efficiency with a high accuracy.
On the other hand, in the rotation rate measuring device mentioned hereinbefore for measuring the rotation rate of a machine with at the non-contact state, a signal corresponding to the rotation period of the rotation body 7 to be measured is extracted to be subjected to the Fourier transform, so that the rotation frequency f0 is specified from the frequency distribution. In this device, in the case that the distribution of the rotation frequency f0 is ideally large as shown in FIG. 33, it is possible to specify the rotation frequency f0.
However, it is general that the rotation rate of the rotation body finely varies, and as shown in FIG. 34, the rotation rate of the rotation body owns a distribution having a center in the rotation frequency f0. In the case of such frequency distribution, it is difficult to specify the rotation frequency f0, thus providing a problem such that the rotation rate and the torque cannot be calculated with a high accuracy by using the mathematical equations (1) and (2). Further, the described device involves a problem such that it is not possible to calculate the torque by obtaining the rotation rate for every rotation in principle in order to specify the rotation frequency f0 from the frequency distribution.
Accordingly, an object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a torque measuring device for obtaining a rotation frequency for every rotation with a measuring accuracy higher than lOns with respect to a rotation member or body to be measured, of which the rotation rate varies minutely.
Another object of the present invention is to provide a torque measuring device capable of measuring axial change direction and axial moving amount and accurately measuring the torque even in a case where the axial change direction and the axial moving amount are different at driving side and loaded side other than the axial direction, or a case where a noise or performance lowering occurs in the device.
These and other objects can be achieved according to the present invention by providing a torque measuring device comprising:
an irradiation means for irradiating a light;
a control means operatively connected to the irradiation means adapted to branch the light into a plurality of lights as beams, control a beam diameter of the respective lights and irradiate the lights on a surface of a member to be measured;
a reflecting means including a plurality of reflectors disposed on the surface of said member to be measured so as to change reflection state of the respective lights;
a detecting means including a plurality of detectors for detecting changes of intensities of the respective reflected lights and generating signals thereof; and
a signal processing means for processing the signals from the detecting means and operating a rotation period on the basis of the signals from the detecting means thereby to calculate a torque of said member to be measured.
In preferred embodiments, there is further provided an optical fiber through which the light from the irradiation means is transmitted to the control means.
The reflecting means comprises a low reflector having a reflection coefficient of the reflected light lower than that of the surface of the member to be measured. The reflecting means comprises a reflector including a high reflection area having a reflection coefficient of the reflected light higher than that of the surface of the member to be measured and a low reflection area having a reflection coefficient of the reflected light lower than that of the high reflection area. The reflecting means may include a reflector including a reflection area reflecting the irradiated light from the irradiation means in a direction to a location of the detecting means and a diffusing reflection area reflecting diffusingly at least one portion of the irradiated light from the irradiation means in a direction other than the direction of the detecting means.
The signal processing means is provided with a variable threshold setting means for varying a threshold according to a variation of an output of the detecting means to thereby extract a detection signal.
There is further provided a filtering means for removing a signal component other than the detection signal from the signals outputted from the detecting means, and also provided with a relative processing means for carrying out a relative processing of the output from the detecting means to obtain the torque of the member to be measured.
The detecting means comprise a first detector and a second detector and the first detector is mounted with a measuring means for monitoring the second detector to thereby measure a position change of the second detector. The first detector may be provided with an irradiation member for transmitting a light to the second detector and the second detector may be provided with a position change measuring means which detects the irradiated light and measures the position change of the first and second detectors.
The torque measuring device has a device body which is arranged along a circumferential or axial direction of the member to be measured.
The reflecting means includes the plural reflectors which are formed by directly forming reflection patterns on the member to be measured. Each of the reflectors is formed of a reflector member having high reflection amount having a length substantially the same as a circumferential length of the member to be measured and which is wound therearound, the reflector member being formed, at a portion thereof, with a low reflection area having less reflection light. The reflection pattern is a bar code pattern in which the low reflection area having less reflection light are formed in shape of plural lines to the reflector member having high reflection amount. The low reflection area has a shape variable along an axial direction of the member to be measured.
The control means comprises a plurality of beam controllers which are arranged in a plurality of pairs so that beam controllers of each pair oppose to each other at an angle of 18020  with the member to be measured being interposed therebetween.
As described above, according to the present invention, a light (beam) control means branches the irradiated light, which is capable of being measured in the inside of a machine or like to be measured or a narrow portion and is transmitted through an optical fiber or a space, into a plurality of the lights, and the beam control means controls a beam diameter of each light so as to be several xcexcm. Then, the beam control means can irradiate the light on the member to be measured.
The reflecting means is composed of a plurality of reflectors which are disposed on the member to be measured to change the reflection state, so that a plurality of detecting means can obtain a plurality of pulse signals having a sharp rising time, a sharp lowering time and a specific shape of the waveform for every rotation.
A signal processing means performs the signal processing in consideration of the output variations with respect to the plural pulse signals having sharp rising and lowering times and the specific waveform, and the signal processing means also performs a mathematical operation of the rotation period and the torque with a desired high accuracy, which is higher than 10 ns.
Furthermore, according to the present invention, the reflector has a structure that the reflecting patterns are directly formed on the member to be measured and the reflector has high reflection amount having a length being the same as the length in the circumferential direction of the member to be measured, so that it is possible to provide a plurality of reflectors in parallel with the rotational axis of the member without being influenced by the size, the shape, the material and the state of the surface of the member or body to be measured. Thus, it is possible to measure the torque of the measured member with high accuracy even in the movement in the axial direction during the rotation of the measured member. Further, it is also possible to prevent a plurality of reflectors from being detached from the measured member by the use condition and an ambient condition of the member or body to be measured.
According to the preferred embodiments, in addition to the above effective functions, by using the optical fiber, the light beam can be transmitted to a portion inside a machinery or narrow space. By providing the reflector having low reflection coefficient to the member to be measured, the reflected light irradiated for a constant time for every rotation thereof can be made extremely small, and hence, the pulse signal having extremely short rising time can be obtained for every rotation. Further, the reflector having an area for reflecting and absorbing the light with a high efficiency minutely varies the intensity of the light irradiated for a constant time for every rotation.
The location of the variable threshold setting means makes it possible to extract the pulse signal considering the output variation of the detected signal.
The location of the filtering device can remove the noise component from the output signal from the detection means.
Furthermore, by performing the relative processing of the pulse signal for every rotation, the rotation period can be measured at a high accuracy, and the torque can be calculated by the delay time from the pulse signal generated from the detection means.
Through the monitoring of the second detector mounted to the first detector, the positional changes thereof due to vibration or impact can be measured, thus reducing the lowering of the torque measurement performance.
A plurality of measuring devices may be disposed along the circumferential direction of the member to be measured, and torques measured by these devices are averaged, thus improving the measurement performance.
The formation of reflection patterns on the member to be measured makes it possible to form the reflector in various shapes, dimensions or like and hence prevents the reflector from being peeled off or likely removed. The ref lector may be formed as bar code, and in this case, the operation processing of the shaft torque can be performed at a high precision by the signal processor even in a case where noise or performance deterioration is caused to the torque measurement device.
Furthermore, since the low reflection area has a shape variable along the axial direction of the member to be measured, the positional change of the beam irradiation can be detected, so that the moving amount and the moving direction of the member in the axial direction can be obtained.
Still furthermore, the location of the plural beam controllers in the opposed arrangement can correct the measurement error and, hence, the torque can be precisely measured.